This section endeavors to supply a context or background for the various exemplary embodiments of the invention as recited in the claims. The content herein may comprise subject matter that could be utilized, but not necessarily matter that has been previously utilized, described or considered. Unless indicated otherwise, the content described herein is not considered prior art, and should not be considered as admitted prior art by inclusion in this section.
Au(evaporated film)-semiconductor(substrate) systems have been studied by Auger electron spectroscopy. For semiconductors with energy gaps (Eg) smaller than ˜2.5 eV, even at room temperature a fraction of atoms constituting the semiconductors were found to accumulate on the surfaces of Au films, indicating ready interfacial interaction between the materials. Study of the interface regions of the systems verified the occurrence of the room-temperature interfacial reactions. Hiraki et al., “Room-temperature interfacial reaction in Au-semiconductor systems,” Applied Physics Letters, Vol. 31, No. 9, pp. 611-612 (Nov. 1, 1977).
The metallurgical interaction at the interface between single-crystal silicon substrates and thin films of elemental platinum have also been examined. This study identified the existence of a 30-Å-thick layer of intermixed Platinum and Silicon which forms at the metal-silicide interface when 50 Å of Pt is electron beam evaporated onto room-temperature Si. The interfacial layer is evident in the high-resolution cross-sectional transmission electron microscopy (HRXTEM) as a uniform band of dark and noncrystalline contrast. In Auger sputter profiling, the evolution of the Si LVV line shape indicated the presence of a Platinum silicide region adjacent to the film/Si interface but not at the surface of the Pt film. Abelson et al., “Disordered intermixing at the platinum: silicon interface demonstrated by high-resolution cross-sectional transmission electron microscopy, Auger electron spectroscopy, and MeV ion channeling,” J. Appl. Phys., Vol. 63, No. 3, pp. 689-692 (Feb. 1, 1988).
Another study considered an interfacial intermixed Pt—Si layer formed during Pt sputtering at room temperature with a subsequent selective etch to form ultrathin PtSi layers. The etching, performed after the metal deposition, removed Pt at fast rates. The etch rate was slowed when the Pt—Si interfacial layer was reached and an oxide was formed on top of the intermixed Pt—Si layer, preventing further etching. During the process, a short-range diffusion technique was believed to transform the intermixed Pt—Si layer into a 3 nm thick continuous PtSi film. A subsequent annealing resulted in a more uniform grain size distribution, without changing the other characteristics of the film. The silicide formed was insensitive to sputter conditions such as sputter power and time. Donaton et al., “New Technique for Forming Continuous, Smooth, and Uniform Ultrathin (3 nm) PtSi Layers,” Electrochemical and Solid-State Letters, Vol. 2, No. 4, pp. 195-197 (1999).